The invention concerns a connecting arrangement.
Particularly in situations involving parts of plastics material, there is frequently a need for the parts in question to be connected together in a simple fashion, by one part being inserted by a relative movement through an opening in the other part. At the end of the relative movement which takes place in that case, as between the two parts, and thus in the relative limit position thereof, the arrangement made up of the two parts produces a retaining or snap connection which is effective at least in one direction and which involves positively locking engagement between the first and second parts such as to prevent the connection from coming loose. Connecting arrangements of that kind are particularly appropriate or necessary when the connections have to be made in an area to which access can only be achieved with difficulty. That may involve for example the interior of a container, or locations on motor vehicles which involve difficult access but in which a component has to be fitted and a connection has to be formed. In such a situation, not least also in regard to the possible difficulty of access, the retaining or snapping connection upon relative insertion of one part into the other part which for that purpose is provided with an opening should occur automatically, with the edges of the opening being able to serve as a guide means during the relative displacement as between the two parts of the connecting arrangement to make the connection.
Connections of that kind which involve the insertion of one part through an opening in another part and in which the positively locking engagement between the two parts in the connecting position is produced by a retaining or detent action are used in particular in connection with components consisting of plastic material, as the elements which co-operate with each other in the retaining or detent engagement condition can generally be integrally formed on plastic components to be connected together, in the process of producing such components, and thus do not involve separate manufacture with its attendant costs. In addition the properties of plastic materials are generally advantageous in regard to retaining or detent connections of that kind, as in particular thermoplastic materials afford the elastic deformability required therefor.
It will be noted however that retaining or detent connections of that kind require the two parts which are to be joined together to be relatively accurately positioned in their relative positions in which they are to be brought into retaining relationship, at any event when that connection is effective only in one direction, while relative movement in the other direction is prevented by a stop which is carried by or formed by another component. In many situations of use however it is difficult to satisfy that requirement as it is not always possible to predetermine with a sufficient degree of accuracy, the extent to which one part of the connecting arrangement is relatively inserted into the other part before the two parts have reached their relative end position, and whether snapping engagement to provide the retaining or detent relationship between the two parts occurs precisely in that end position, which is defined for example by a wall or another component. Difficulties in that respect may arise in particular if at least one of the two parts to be connected together, or the above-mentioned other component which defines the relative end position of the two parts, comprises plastic material because in particular some thermoplastic materials, after molding thereof, in particular in the cooling phase, suffer some distortion or can experience certain changes in configuration due to other influences. The tolerances which are caused by such subsequent variations and which cannot be readily foreseen in regard to their occurrence and the magnitude thereof may admittedly be very slight, but they are frequently sufficiently great to cause the connecting arrangement to move into its condition of retaining or detent engagement before the one part of the connecting arrangement has reached its desired or target end position, relative to the other part thereof. That can mean for example that the connection still allows a certain amount of play between the two parts, after the connection therebetween has been formed. Such play is frequently undesirable even if the durability thereof is not adversely affected as a result, as the play, even if it is very slight, can result in banging or rattling noises, for example in the case of parts which are fitted in a motor vehicle. There is also the point that in the majority of cases the situation in any case requires the parts to co-operate with each other, in their connected condition, in such a way that they cannot perform uncontrolled movements relative to each other. On the other hand, when such inaccuracies occur, there is also the possibility that the part whose end position is determined by the above-mentioned other component acting as a stop has already reached the end position of the connecting arrangement be fore the retaining or snap-engagement connection has moved definitively into its operative position so that in fact the two parts are not locked together at all.